如何交换二维数组的行和列？

huangapple
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英文:

How to swap rows and columns of a 2d array?

问题

我正在尝试编写一个用于“转置”二维整数数组的方法，其中原矩阵的行和列被交换。

然而，我不知道如何实现这个方法。
我应该如何编写这个方法？

  1. public class Matrix {
  2.     private int[][] numbers;
  4.     public Matrix(int rows, int columns) {
  5.         if (rows < 1)
  6.             rows = 1;
  7.         else
  8.             rows = rows;
  9.         if (columns < 1)
  10.             columns = 1;
  11.         else
  12.             columns = columns;
  13.         numbers = new int[rows][columns];
  14.     }
  16.     public final void setNumbers(int[][] numbers) {
  17.         this.numbers = numbers;
  18.     }
  20.     public int[][] getNumbers() {
  21.         return numbers;
  22.     }
  24.     public int[][] transpose() {
  25.         int[][] transpose = new int[numbers[0].length][numbers.length];
  26.         for (int i = 0; i < numbers.length; i++) {
  27.             for (int j = 0; j < numbers[0].length; j++) {
  28.                 transpose[j][i] = numbers[i][j];
  29.             }
  30.         }
  31.         return transpose;
  32.     }
  33. }
英文:

I'm trying to write a method for 'transpose' a two-dimensional array of integers, in which the rows and columns of the original matrix are exchanged.

However, I have no idea how I can realize this.
How do I write out this method?

  1. public class Matrix {
  2.     private int[][] numbers;
  4.     public Matrix(int rows, int colums) {
  5.         if (rows &lt; 1)
  6.             rows = 1;
  7.         else
  8.             rows = rows;
  9.         if (colums &lt; 1)
  10.             colums = 1;
  11.         else
  12.             colums = colums;
  13.         numbers = new int[rows][colums];
  14.     }
  16.     public final void setNumbers(int[][] numbers) {
  17.         this.numbers = numbers;
  18.     }
  20.     public int[][] getNumbers() {
  21.         return numbers;
  22.     }
  24.     public int[][] transpose() {
  25.         int[][] transpose = getNumbers();
  26.         return numbers;
  27.     }
  28. }

答案1

得分: 8

你可以遍历行和列，并将每个元素[i,j]赋值给转置的[j,i]：

  1. /**
  2.  * 转置矩阵。
  3.  * 假设：mat是一个非空矩阵，即：
  4.  * 1. mat != null
  5.  * 2. mat.length > 0
  6.  * 3. 对于每个i，mat[i].length相等且mat[i].length > 0
  7.  */
  8. public static int[][] transpose(int[][] mat) {
  9.     int[][] result = new int[mat[0].length][mat.length];
  10.     for (int i = 0; i < mat.length; ++i) {
  11.         for (int j = 0; j < mat[0].length; ++j) {
  12.             result[j][i] = mat[i][j];
  13.         }
  14.     }
  15.     return result;
  16. }
英文:

You could iterate over the rows and columns and assign each element [i,j] to the transposed [j,i]:

  1. /**
  2.  * Transposses a matrix.
  3.  * Assumption: mat is a non-empty matrix. i.e.:
  4.  * 1. mat != null
  5.  * 2. mat.length &gt; 0
  6.  * 3. For every i, mat[i].length are equal and mat[i].length &gt; 0
  7.  */
  8. public static int[][] transpose(int[][] mat) {
  9.     int[][] result = new int[mat[0].length][mat.length];
  10.     for (int i = 0; i &lt; mat.length; ++i) {
  11.         for (int j = 0; j &lt; mat[0].length; ++j) {
  12.             result[j][i] = mat[i][j];
  13.         }
  14.     }
  15.     return result;
  16. }

答案2

得分: 1

矩阵的转置

  1. int m = 4;
  2. int n = 5;
  1. // 原始矩阵
  2. int[][] arr1 = {
  3.     {11, 12, 13, 14, 15},
  4.     {16, 17, 18, 19, 20},
  5.     {21, 22, 23, 24, 25},
  6.     {26, 27, 28, 29, 30}};
  8. // 转置矩阵
  9. int[][] arr2 = new int[n][m];
  1. // 交换行和列
  2. IntStream.range(0, n).forEach(i ->
  3.         IntStream.range(0, m).forEach(j ->
  4.                 arr2[i][j] = arr1[j][i]));
  1. // 输出到 Markdown 表格
  2. String matrices = Stream.of(arr1, arr2)
  3.         .map(arr -> Arrays.stream(arr).map(Arrays::toString)
  4.                 .collect(Collectors.joining("<br>")))
  5.         .collect(Collectors.joining("</pre> | <pre>"));
  7. System.out.println("| 原始矩阵 | 转置矩阵 |");
  8. System.out.println("|---|---|");
  9. System.out.println("| <pre>" + matrices + "</pre> |");
原始矩阵 转置矩阵 
  1. [11, 12, 13, 14, 15]
    [16, 17, 18, 19, 20]
    [21, 22, 23, 24, 25]
    [26, 27, 28, 29, 30]
 
  1. [11, 16, 21, 26]
    [12, 17, 22, 27]
    [13, 18, 23, 28]
    [14, 19, 24, 29]
    [15, 20, 25, 30]

另请参阅：使用数组打印蛇形图案

英文:

The transpose of a matrix

  1. int m = 4;
  2. int n = 5;
  1. // original matrix
  2. int[][] arr1 = {
  3.         {11, 12, 13, 14, 15},
  4.         {16, 17, 18, 19, 20},
  5.         {21, 22, 23, 24, 25},
  6.         {26, 27, 28, 29, 30}};
  8. // transposed matrix
  9. int[][] arr2 = new int[n][m];
  1. // swap rows and columns
  2. IntStream.range(0, n).forEach(i -&gt;
  3.         IntStream.range(0, m).forEach(j -&gt;
  4.                 arr2[i][j] = arr1[j][i]));
  1. // output to the markdown table
  2. String matrices = Stream.of(arr1, arr2)
  3.         .map(arr -&gt; Arrays.stream(arr).map(Arrays::toString)
  4.                 .collect(Collectors.joining(&quot;&lt;br&gt;&quot;)))
  5.         .collect(Collectors.joining(&quot;&lt;/pre&gt; | &lt;pre&gt;&quot;));
  7. System.out.println(&quot;| original matrix | transposed matrix |&quot;);
  8. System.out.println(&quot;|---|---|&quot;);
  9. System.out.println(&quot;| &lt;pre&gt;&quot; + matrices + &quot;&lt;/pre&gt; |&quot;);
original matrix transposed matrix
<pre>[11, 12, 13, 14, 15]<br>[16, 17, 18, 19, 20]<br>[21, 22, 23, 24, 25]<br>[26, 27, 28, 29, 30]</pre> <pre>[11, 16, 21, 26]<br>[12, 17, 22, 27]<br>[13, 18, 23, 28]<br>[14, 19, 24, 29]<br>[15, 20, 25, 30]</pre>

<sup>See also: Printing a snake pattern using an array</sup>

huangapple
  • 本文由 发表于 2020年8月10日 14:06:21
  • 转载请务必保留本文链接：https://go.coder-hub.com/63334942.html
  • arrays
  • java
  • matrix
  • multidimensional-array
  • transpose
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